Usage of printf for cyw43-spi

[felixdoerre]

Currently the cyw43 spi implementation has a hard dependency on printf, here (and another one a few lines lower).

https://github.com/raspberrypi/pico-sdk/blob/master/src/rp2_common/pico_cyw43_driver/cyw43_bus_pio_spi.c#L501

I suggest to replace these printf-calls with the CYW43_PRINTF macro already available in cyw43-code, so binaries that include the cyw43 driver and don't require printf are not forced to pull it in.